The use of non-silver halide high resolution photosensitive plates for the production of microelectronic components has become quite prevalent in recent years. These plates generally comprise a stable transparent substrate, such as glass, and a coating of a thin uniform layer of a volatile, preferably organic, solvent solution of a resin adapted to form an adherent transparent film upon evaporation of the solvent. The coating contains a photo-sensitizing composition comprising an azo coupling component and a light sensitive diazonium compound susceptible of decomposition upon exposure to actinic light. The composition is temporarily stabilized against coupling pending development of the latent image.
After exposure to actinic light through a primary mask bearing the desired pattern of a microelectronic device to be reproduced, the plate is developed by treatment with moist ammonia vapor. To facilitate such treatment, various types of developing apparatuses have been provided in which to properly expose the sensitized plates to wetted ammonia to develop the image thereon. Available developing devices often comprise merely a container or housing formed of plastic material adapted to receive therein a large plurality of exposed diazo plates, and an opening in which moisturized ammonia is introduced from an exterior source. Unfortunately, the use of these simple containers requires additional means remote therefrom for moisturizing ammonia vapor, and condensing ammonia droplets from the wetted ammonia vapor. As a result, prior developing apparatuses of this type require elaborate set-up arrangements to avoid the danger of inadequate seals and connections between the various components and the possibility of ammonia leakage to the surrounding environment.
To overcome these difficulties and provide a useful, efficient developing apparatus for diazo photo-sensitive plates, a substantially unitary developing apparatus has been provided by Czebiniak in U.S. Pat. No. 3,982,258. The apparatus disclosed in such patent is generally formed by a single housing having a humidity conditioning chamber containing concentrated ammonia hydroxide liquid through which ammonia gas from an external source, i.e. bottled anhydrous NH3, may be bubbled to raise its moisturization level, a condensation chamber adjacent the humidity conditioning chamber to remove liquid ammonia droplets, means connecting the humidity conditioning chamber to the condensation chamber, a developing chamber adjacent the condensation chamber for accomodating a plurality of plates to be developed by exposure to the moisturized ammonia, and means connecting the developing chamber with the condensation chamber for supplying moisturized ammonia thereto. A sealable cover or door is provided to gain access to the developing chamber for the insertion and removal of sensitized plates. Conduit means are connected to the developing chamber for supplying pressurized dry air or nitrogen from another external source in order to flush the chamber of residual ammonia after developing.
While the aforementioned Czebiniak developing apparatus has generally been found to be satisfactory, under certain conditions it has been found that the humidity level of the anhydrous ammonia is not raised sufficiently by bubbling through the ammonium hydroxide, resulting in poor quality development. Moreover, the ammonia vapor does not always circulate thoroughly within the developing chamber since such circulation depends entirely upon the pressure imparted to the gas by the external anhydrous ammonia bottle. As the pressure within the bottle is reduced, circulation becomes impaired. In addition, it has been found that such developing apparatus cannot be utilized in many industrialized nations, particularly those in Europe, since the use of bottled anhydrous ammonia is either prohibited or requires costly licenses and insurance.
Other diazo type developing means, particularly for photocopy machines, have previously dealt with the problem of circulating sufficient gaseous ammonia within a developing chamber and subsequently evacuating such ammonia from the chamber upon completion of the development process. Such a device is shown in U.S. Pat. No. 3,900,862 to Bennett, et al. The apparatus disclosed in such patent comprises a developing chamber for receiving exposed diazo-type sensitized paper, means for introducing and circulating gaseous ammonia within the chamber to develop an image on the sensitized paper and a vacuum pump for evacuating the ammonia from the developing chamber. A portion of the ammonia which is evacuated from the developing chamber is recirculated through a reservoir containing ammonium hydroxide, and the balance is discharged into an absorption chamber containing an ammonia absorbing agent, such as citric acid. While the Bennett, et al. developing apparatus is most suitable and quite satisfactory for developing diazo-type sensitized paper for photocopy purposes, it is inadequate for developing high resolution sensitized diazo plates, since it makes no provision for adequately moisturizing the ammonia. Moreover, while the quantity of gas circulated within the developing chamber is sufficient for developing sensitized photocopy paper, it is insufficient to adequately reproduce the image on the high resolution plates referred to above.